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The D20A "Gemini" is a distinctive side-by-side 2xAA light from Sunwayman. In addition to this rather unusual configuration, it also has dual emitters  a standard Cool White XP-G2 for the main beam, and a secondary red XR-E LED.

Let's see how it performs

Manufacturer Reported Specifications:
(note: as always, these are simply what the manufacturer provides  scroll down to see my actual testing results).

Aerospace-grade aluminum alloy, Stainless Steel retaining ring on the top

Military Specification Type III- hard anodized body

Waterproof, in accordance with IPX-8 standard

Ultra-clear tempered glass lens resists scratches and impacts

Dimensions: 21mm x 35mm x 102.5mm

Weight: 119g excluding battery

Accessories: Lanyard, O-ring

MSRP: ~$83

The D20A comes in the standard Sunwayman display-style cardboard box with product information printed right on the package. Inside you get a wrist lanyard, extra o-rings, manual and product inserts. There is no belt pouch, but a pocket clip comes attached to the light using two Hex screws.

The appearance of the D20A is pretty distinctive  it reminds me of my old Duracell Durabeam 2xAA from the mid-80s. Ah, memories.

The side-by-side arrangement makes this light quite compact, although battery changing is little more complicated. You'll note the main white emitter on the upper part of the front, and the red LED (under a red dome) just below it.

There also dual electronic switches, located side-by-side near the head. The lower on/off one is slightly less raised than the mode-changing one above it.

The switches have about typical feel for electronic switches, which means accidental activation is a possibility. I would think these would be hard to find by touch with gloves on. Scroll down for a discussion of the UI.

As with several other recent Sunwayman lights, the light comes in black anodizing, type III (hard anodized), in a matte finish. Personally, I miss the dark gray natural finish anodizing of old. As always, all labels are bright white against the dark background.

There is no real knurling to speak of on the D20A, but there are a number of fine gradations all along the body and tail. The effect is somewhat similar to the recent Fenix lights that use a similar design. The pocket clip is very firmly attached, and holds on stiffly to the light. Note that some of the edges are a bit sharp (i.e., around the tailcap and the main body cut-outs).

The light opens at the tailcap.

Design here is unusual, as you have to turn the lock piece a quarter turn to unlock/re-lock the tailcap in place. There is a small half-moon handle on the lock that flips loose when the light is held pointing up. Tension is significant, and it takes a little practice to be able to do this smoothly. This makes battery changes a bit of a pain  certainly not something that you will want to do with gloves on, or in the dark.

Pay attention to the correct orientation of cells.

There is a stainless steel bezel for the main white emitter.

The main reflector is smooth. XM-G2 cool white emitter was well centered on my sample.

Sunwayman confirms that there is an actual red XP-E LED under there (hard to tell with the red dome). In the absence of a reflector, the convex optic helps to focus light into a defined beam (scroll down for beamshots).

User Interface

Turn the white light on by clicking the lower electronic switch (i.e. a quick press and release, from off, of the bottom switch). Click again to turn the light off. Turn the red light on by pressing and holding the lower switch (from off). Again click to turn off.

There are four main output levels of constant white light, selected by clicking the upper mode switch when on. The light will advance through all the levels in the following repeating sequence: Turbo > Hi > Med > Lo.

There are two flashing modes of white light, selected by either double-clicking the upper mode switch (for Strobe), or pressing and holding the upper mode switch (for SOS). A single click of the mode switch returns you to constant on.

For the red light, you similarly click the upper switch again to change modes (after turning the red light on). The level sequence is Hi > Med > Lo > Police Strobe, in a repeating loop.

There is one additional flashing mode for the red light, selected by pressing and holding the mode switch when on (for Slow Flash). A single click of the mode switch returns you to constant on.

The light has level memory, but only for the current mode. So for example, if you turn the light off in the white Lo mode, and then re-active (in white), you will get Lo again. But if you re-activate in red, the white level memory is erased and the new red level is saved upon turning off the light. Note also that the default level is max output, for either mode (i.e., when you switch to the other color, it first activates in max).

As this is an electronic switch, a standby current is required (see below for measurements). To lock out the light, from off, press and hold the upper mode button for more than 2 seconds. The main emitters will flash briefly, and the light is not locked out. To unlock, repeat the same procedure.

Video:

For information on the light, including the build and user interface, please see my video overview:

Video was recorded in 720p, but YouTube typically defaults to 360p. Once the video is running, you can click on the configuration settings icon and select the higher 480p to 720p options. You can also run full-screen.

As with all my videos, I recommend you have annotations turned on. I commonly update the commentary with additional information or clarifications before publicly releasing the video.

PWM/Strobe

As with most of my Sunwayman lights, I don't see any signs of pulse width modulation (PWM) on the lower output modes. There is some measurable circuit noise on my D20A, in some modes  although it is not visible to the eye:

White Turbo/Hi Noise:

I only see very faint circuit noise on the Turbo white mode, around 2 kHz or so. This noise is in no way visible to the eye in use.

Red Hi Noise:

Red Med Noise:

Red Lo Noise:

There is a strong reoccurring signal on the Med/Hi levels of the Red light, but at a non-visible 4.9 kHz. It does not have the typical PWM pattern, but it is of sufficient strength on these modes as to be visible when shining on a fan.

Take home message: you don't generally need to worry about the oscilloscope-detectable noise patterns. The frequency is high enough that you will not see them by eye (i.e., I detected no visual flicker, on any mode).

White Strobe:

The main strobe is a high frequency ~16 Hz strobe. Very disorienting.

White SOS:

The D20A has a typical SOS mode.

Red mode Strobe:

The red strobe is a "police strobe" (basically a signaling strobe, as if for traffic use). You get four pulses (at ~11 Hz frequency) every ~1.7 secs or so.

The Slow Flash of the red mode is a 1 second on, 1 second off slow flash.

Standby Drain

As the switch is an electronic one, a standby current drain is always present when a battery is installed.

When I first connect my DMM, I measured an initial current of ~280uA (on two NiMH AA cells). However, after a few seconds, the stand-by drain dropped to 9.3uA, and remained there stably. Given the serial cell arrangement, this would translate into over 24 years before 2000mAh NiMH batteries would be drained. It is definitely negligible, and not a concern.

Sunwayman provides an electronic lock-out mode that is activated by a sustain press of the mode switch from off, for more than 2 seconds (see UI section).

Beamshots:

For white-wall beamshots below, all lights are on Max output on 2x Sany Eneloop NiMH (2000mAh) batteries. Lights are about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.

The D20A has a reasonable beam pattern. It is not as throwy as most of the XP-G/XP-G2-based 2xAA lights, due to the smaller reflector.

The red beam is interesting  there is no real hotspot to speak of, just a fairly even smooth beam with a sharp spillbeam edge. The red convex dome seems to help maintain a clear demarcation of the spill.

Testing Method:

All my output numbers are relative for my home-made light box setup, as described on my flashlightreviews.ca website. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

As you could tell from the beamshots, max output is generally in keeping with the lower range of recent 2xAA lights (i.e., similar to some of the earlier XP-G lights in this class). But it is still a good amount of output. As previously mentioned, peak throw is somewhat reduced from other XP-G/XP-G2 lights, due to the smaller reflector.

My peak intensity throw and beam distance measures are very consistent with Sunwayman ANSI FL-1 specs. Let's see how the lumens estimates do across all levels.

Again, my lumen estimates are very close to Sunwayman's output specs, at least on white. My lightbox seems to read the red modes as a little higher.

Output/Runtime Graphs:

Let's start with a comparison of the Med-Turbo modes, on both emitters:

As you can see, on Turbo (white LED) the light steps down after ~3.5 mins to the defined Hi mode. Overall runtime is thus fairly similar between Turbo and Hi.

The red LED has lower overall output and runtime, in keeping with the lower output XP-E emitter (and additional red dome, which likely further cuts output). It also shows a less tightly-regulated pattern.

Let's see how it compares to the competition:

Performance on Hi is quite reasonable for the class, on all levels tested. The real stand-out is the alkaline runtime, where the D20A manages to squeeze out an impressive amount of runtime on Hi.

In contrast, the Med mode is about typical (or toward the lower end) of the XP-G/XP-G2 class, on the batteries tested.

Potential Issues

The tailcap has a fair amount of pressure to seat properly, and the lock mechanism has a very thin handle. It is definitely a two-handed job, and would not be feasible with gloves on.

The electronic switches are small, and may be hard to access with gloves on. User interface may take a little getting used to. Accidental switch activation is possible, so I recommend you store the light with the electronic lock-out activated.

Mode memory is not independently maintained for the two emitters modes (i.e., only one common memory store for last mode/output level used).

The edges of the light are fairly sharp, especially around the tailcap and body cut-outs.

Preliminary Observations

The D20A is a distinctive form factor  you don't see many side-by-side 2xAA lights ("Gemini" indeed). It really brings me back to an earlier decade. There are some definite advantages to this sort of design, although it also creates a few challenges.

Overall, I find ergonomics and hand feel to be fairly good (despite a few sharp edges). It is certainly very compact for a 2xAA light (thanks to side-by-side battery arrangement), making it easy to slip into a jacket pocket or bag. The included pocket clip is pretty stiff, and should hold securely. However, battery changes can be a bit fussy with the locking tailcap (and certainly could not easily be done in the dark, or with gloves on).

In general terms, the features of the light are very similar to the recent Sunwayman C21C "Thunder Hammer". The main differences are the dual switch design here (which is appreciated), and the lower overall output levels (including a lower Lo, which is also appreciated). Beam pattern on the white emitter is relatively more "throwy" (but with less max output), due to the XP-G2. The red flood light is very similar, with its distinctive spot-beam like optic. Please see my review of that light for more comments on the red beam.

The dual switches provide for a more intuitive interface on the D20A compared to single-switch C21C. I am glad to see the easy access electronic lock-out, although this could be over-come accidentally (i.e., only needs a 2 secs sustained Mode button press to lock/unlock). And unfortunately, the common memory position of the C21C is maintained here as well (i.e., you lose the other mode memory when switching between emitters).

Output/runtime performance is good, consistent with a current-controlled circuit. Note that the D20A uses a XP-G2, and is not as heavily driven as some recent 2xAA lights.

The D20A is a fairly unique light in my testing, and one with a versatile feature set thanks to the secondary red LED. The side-by-side battery design has a definite appeal in principle, although it does complicate the tailcap design. Still, it is always nice to see something different. I'm curious to hear what the members here think of this arrangement.

nice review. How wide is red beam? Surely there must be some loss of light with the red lens?

It is narrow. I haven't taken measures at a distance, but you can a relative feel from the white wall beamshots (all done at the same distance), and from the video.

Alkaline battery runtime is very impressive even though the graph is not absolutely flat. I wonder if you'll get a similar graph with another set of batteries?

Yes, it is an impressive finding. I may try to do a second runtime with another batch of alkalines... although in my experience, there typically isn't that much variation in runtime on the same sample, run on batteries from the same lot.

Thank you for an excellent product review. Based upon your review I purchased one for a XMAS gift
for a relative who is in the NAVY. The red led will allow him excellent night vision when on board
ship. Also using two AA batteries makes it easy to locate and replace as needed.

I agree the grip could have smoother corners and more knurling.

The method to secure the battery cover is indeed a bit challenging but with use
I assume you can become quite agile at opening and closing the rear cap.

Bought myself one for Christmas and very happy with it. Only trouble is that the red beam is square with rounded edges and slightly off centre with the light. I'll have to play with the lens.
Surprisingly heavy and solid light. There is some sharpness to the battery cover corners but not as bad as I expected from previous comments.